fix: answer new prompts when updating child repositories

[mjun0812]

Overview and Background

Pushing the v2.0.0 tag ran the template distribution workflow, and its Update template in child repository step failed:

🎤 Which license do you want to use? Choose None to keep the project unlicensed.
Interactive session required: Use `--defaults` and/or `--data`/`--data-file`

copier update -A skips questions that already have a recorded answer, but the license prompt added in #34 is absent from .copier-answers.yml in any repository generated before it. With no answer to reuse and no terminal, Copier aborts. The Release workflow itself succeeded, so v2.0.0 exists; only the propagation to child repositories failed.

The repository's own Template lifecycle job did not catch this because it called copier update with --defaults, which answers new prompts, while the distribution workflow did not.

Related Issues

None. Regression from the license prompt added in #34.

Implementation Approach

• Add --defaults to the distribution workflow's copier update. Prompts added since the child repository was last updated take their default value; every previously answered question still keeps the child's own answer because -A remains in place. This is the resolution Copier's own error message points to, and it keeps working for any prompt added in the future.
• Give the Template lifecycle CI job the same flag set (-A --defaults --trust) so the path exercised in CI matches the one that actually reaches child repositories.

The workflow opens a pull request rather than pushing, so a person still reviews whatever the defaults produced before it lands in a child repository.

Changes

• .github/workflows/trigger-template-update.yml: copier update -A --defaults --trust, with a comment explaining why --defaults is required.
• .github/workflows/test.yml: lifecycle job uses the same flags, with a comment tying the two commands together.

Impact

• Child repositories updating from v2.0.0 onward receive license: MIT (the prompt's default) unless they answer otherwise. Their pyproject.toml gains license = "MIT" and license-files = ["LICENSE"]. A LICENSE file is created only when the repository does not already have one, because LICENSE is listed in _skip_if_exists. A repository that wants a different license can edit .copier-answers.yml before merging the generated pull request, or edit the pull request itself.
• No change to generated project contents, the template, or the Release workflow.

Validation Results

Reproduced the failure and verified the fix against a child repository generated from the v1.0.0 tag and committed as a git repository, mirroring what the workflow does.

# Before: the exact command the workflow ran
uvx copier update -A --trust < /dev/null
# Updating to template version 2.0.0
# Warning: Input is not a terminal (fd=0).
# Interactive session required: Use `--defaults` and/or `--data`/`--data-file`

# After: the command from this PR
uvx copier update -A --defaults --trust < /dev/null
# Updating to template version 2.0.0        (completes, exit 0)
grep -E '_commit|license|python_version' .copier-answers.yml
# _commit: v2.0.0
# license: MIT
# python_version: '3.13'      <- pre-existing answer preserved, not reset to the new 3.14 default
git status --short | wc -l    # 26 changed or added files

Also ran the Template lifecycle job's steps locally with the new flags: generate from v1.0.0, commit, update to HEAD, assert a diff and a changed _commit, then uv build.

diff produced and revision updated: ok
Successfully built dist/lifecycle_project-0.0.1-py3-none-any.whl
build artifacts: ok